from math import sqrt, pow

x1, y1, x2, y2 = list(map(float, input().split()))
print(sqrt(pow(x1 - x2, 2) + pow(y1 - y2, 2)))
 from math import sqrt, pow x1, y1, x2, y2 = list(map(float, input().split())) x1 list(map(float, input().split())) list map(float, input().split()) map float input().split() ().split () input split y1 x2 y2 print(sqrt(pow(x1 - x2, 2) + pow(y1 - y2, 2))) print sqrt(pow(x1 - x2, 2) + pow(y1 - y2, 2)) sqrt pow(x1 - x2, 2) + pow(y1 - y2, 2) pow(x1 - x2, 2) pow x1 - x2 x1 x2 2 pow(y1 - y2, 2) pow y1 - y2 y1 y2 2 y2 = list(map(float, input().split())) list(map(float, input().split())) y2 x1, y1, x2, y2 = list(map(float, input().split())) list(map(float, input().split())) x1 y1, x2, y2 = list(map(float, input().split())) list(map(float, input().split())) y1 x2, y2 = list(map(float, input().split())) list(map(float, input().split())) x2
from math import sqrt, pow

x1, y1, x2, y2 = list(map(float, input().split()))
print(sqrt(pow(x1 - x2, 2) + pow(y1 - y2, 2)))

